Problem while downloading a magazine

I bought a magazine through this app and it simply does not download it as supposed to. I have tried downloading it many times but it doesnt work. I keep facing a message that says a problem gas occured and I should restart the app.
I also couldnt easily find a support page where I could get a solution for my problem. I really hope somebody will get it fixed.

Julianomol about Harvard Business Review Intl, v2.5.5